Method of treating insulin resistance

ABSTRACT

The invention relates to methods of treating insulin resistance in mammals, preferably in humans, which methods comprise administering to a mammal in need thereof an effective amounts of succinic acid or a pharmaceutically acceptable salts thereof.

TECHNICAL FIELD

The present invention is in the field of medicine, particularly in thetreatment of states of insulin resistance that can result from disorderssuch as dibetes mellitus and its chronic complications such asretinopathy, polyneuropathy, nephropathy, angiopathy; gestationaldiabetes mellitus; impaired glucose tolerance; obesity; aging;atherosclerosis; syndrome X; cardiovascular disease; AIDS; cancer;wasting/cachecxia; sepsis; trauma associated with burns; malnutrition;lupus and other autoimmune diseases; endocrine diseases; hyperuricemia;hyperlipidemia; dyslipidemia; polycystic ovary syndrome; orcomplications arising from athletic activity.

BACKGROUND ART

Succinic acid is the physiologically occurring substrate of succinatedehydrogenase in mammals that play a role in cellular respiration andenergy metabolism.

Insulin resistance is a condition in which the tissues of the body failto respond normally to insulin. DeFronzo, R. A. J. CardiomuscularPharmacology 20 (Suppl. 11): S1-S16 (1992). The insulin resistancemanifesting itself in pathologically elevated endogenous insulin andglucose levels and predisposes to the development of a cluster ofabnormalities, including some degree of impaired glucose tolerance, anincrease in plasma triglycerides and low density lipoprotein cholesterol(LDL) levels, a decrease in high-density lipoprotein cholesterol (HDL)levels, high blood pressure, hyperuricemia, a decrease in plasmafibrinolytic activity, an increase in cardiovascular disease andatherosclerosis. Reaven, G. M. Physiol-Rev. 75(3): 473-86 (1995). Thedecompensated insulin resistance is widely believed to be an underlyingcause of non-insulin dependent diabetes mellitus.

A method of treating insulin resistance is known which comprisesadministration of insulin. Yki-Jarvinen, H. et al. N. Engl. J. Med. 327:1426-1433 (1992). However, a basic disorder in the case of insulinresistance lies in the glucose assimilation by peripheral tissues of amammal body. In this connection, it is important to treat the glucoseassimilation not by the administration of insulin or by thepharmaceutical drug stimulating the excretion of insulin, but by themechanisms independent thereof. Haering H. U., Mehnert H., Diabetologia36: 176-182 (1993).

Free fatty acids induce insulin resistance in human in a dose dependentfashion. Boden G. Front. Biosci. 3, d169-175 (1998); Boden G., Diabetes46(1): 3-10 (1997). Lowering of plasma free fatty acid levels isaccordingly effective in the treatment of insulin resistance in amammal.

Surprisingly, it has now been found that administration of an effectiveamount of succinic acid or salt thereof to insulin resistant mammals iseffective therapy for treating of insulin resistance. Lowering of plasmafree fatty acid levels accompanies a lowering of pathologically elevatedinsulin and glucose levels that reflects an improving in insulinsensitivity. More surprisingly, this biological effect is a long-term,and the best results are achieved in the after-treatment period.

This result is unexpected to Japanese Patent No. 61171417 describingthat dicarboxylic acids including succinic acid are useful asantidiabetics showing promoting action on insulin secretion. Morerecently, MacDonald et al. demonstrated contrary to Japanese Patent No.61171417 data that unesterified succinate, the compound of the presentinvention, did not stimulate insulin release in pancreatic islets butonly esters of succinic acid are potent insulin secretagogues.MacDonald, M. J., Fahien, L. A. Diabetes 37(7): 997-999 (1988).Moreover, promotion of insulin secretion are useful in treating insulindependent diabetic mammals with low or no insulin secretion, whileinsulin resistant mammals including non-insulin dependent diabeticmammals are needed in decreasing of elevated insulin levels rather thanpromotion of insulin secretion.

The present invention shows for the first time that succinic acid orsalt thereof is useful for treating of insulin resistance in mammals,particularly in humans afflicted with non-insulin dependent diabetesmellitus.

It is an object of the present invention to provide the use of succinicacid or a pharmaceutically acceptable salt thereof for the manufactureof medicament or nutritional supplement useful for treating insulinresistance in a mammal.

It is an object of the present invention to provide a method of treatinginsulin resistance in a mammal, comprising administering to the mammalin need thereof of an effective amount of succinic acid or apharmaceutically acceptable salt thereof. Orally, or parenterally, ortopically, or rectally, as a nutritional supplement or medicament.

DISCLOSURE OF INVENTION

The present invention provides a method of treating insulin resistancein a mammal, which comprises administering to a mammal in need thereofan effective amount of succinic acid or a pharmaceutically acceptablesalt thereof. Insulin resistance in the mammal can be associated withdisorders such as diabetes mellitus and its chronic complications suchas retinopathy, polyneuropathy, nephropathy, angiopathy; or gestationaldiabetes mellitus; or impaired glucose tolerance; or obesity; or aging;or atherosclerosis; or syndrome X; or cardiovascular disease; or AIDS;or cancer; or wasting/cachecxia; or sepsis; or trauma associated withburns; or malnutrition; or lupus and other autoimmune diseases; orendocrine diseases; or hyperuricemia; or hyperlipidemia; ordyslipidemia; or polycystic ovary syndrome; or complications arisingfrom athletic activity. More particularly, the present inventionprovides the method of treating insulin resistance in a human afflictedwith non-insulin dependent diabetes mellitus. Succinic acid has thechemical structure given below:

HOOCCH₂CH₂COOH

The pharmaceutically acceptable salt of the succinic acid is prepared byknown methods from organic and inorganic bases. Such bases include, butare not limited to, nontoxic alkali metal and akaline earth bases, forexample, calcium, lithium, sodium, and potassium hydroxide; ammoniumhydroxide and nontoxic organic bases, such as triethylamine, butylamine,diethanolamine, triethanolamine and 2-ethyl-6-methyl-3-hydroxypyridine.

The succinic acid or a pharmaceutically acceptable salt thereof ispreferably administered orally in the method of this invention. Thesuccinic acid or a pharmaceutically acceptable salt thereof may also beadministered by a variety of other routes such as parenterally, e.g.intravenously, subcutaneously, intramuscularly,; topically or rectally.Preferably, the succinic acid or pharmaceutically acceptable saltthereof is administered for a period of 1 day or longer; more preferablyfor a period of 3 to 7 days. The effective amount of succinic acid or apharmaceutically acceptable salt thereof for use in the method of thisinvention is preferably from 0.1 milligram to 50 milligrams per day perkilogram of body weight of the mammalian subject, more preferably from 1mg to 20 mg per day per kilogram of body weight of the mammaliansubject.

Treating, as used herein, describes the managment and care of a mammalfor the purpose of combating the disease, condition, or disorder andincludes the administration of succinic acid or a pharmaceuticallyacceptable salt thereof to prevent the onset of the symptoms orcomplications, alleviating the symptoms or complications, or eliminatingthe disease, condition, or disorder. Treating of insulin resistance in amammal includes increasing insulin sensitivity manifesting itself in alowering of free fatty acid, insulin and glucose levels.

Also provided according to the present invention is the use of succinicacid or a pharmaceutically acceptable salt thereof for the manufactureof a medicament or nutritional supplement useful for treating insulinresistance in a mammal. Preferably, mammal is a human.

The medicaments or nutritional supplements of the invention are preparedby known procedures using well-known ingredients. In making themedicaments or nutritional supplements, the active ingredients willusually be mixed with a carrier, or diluted by a carrier, or enclosedwithin a carrier, and may be in the form of a capsule, tablet, paper orother container. When the carrier serves as a diluent, it may be asolid, semisolid, or liquid material which acts as a vehicle, excipient,or medium for the active ingredient. The nutritional supplements can bein the form of tablets, pills, powders, elixirs, suspensions, emulsions,solutions, syrups, soft and hard gelatin capsules. The medicaments canbe in the form of tablets, pills, powders, elixirs, suspensions,emulsions, solutions, syrups, soft and hard gelatin capsules, aerosoles,suppositories, sterile injectable solutions, and sterile packagedpowders.

Some examples of suitable carriers, diluents, and excipients includelactose, dextrose, sorbitol, mannitol, calcium phosphate, alginates,gelatin, calcium silicate, microcrystalline cellulose,polyvinylpyrrolidone, cellulose, water syrup, methyl cellulose, methyland propyl hydroxybenzoates, talc, magnesium stearate; stearic acid, andmineral oil. The medicaments or nutritional supplements can additionallyinclude lubricating agents, wetting agents, emulsifying and suspendingagents, preserving agents, sweetening agents, or flavoring agents.

Preferably the medicament or nutritional supplement of the invention isin a dosage form and can be administrated orally, or parenterally, ortopically, or rectally.

The medicament or nutritional supplement of the invention can be usedadvantageously in combination with antidiabetic drugs, particularly withinsulin.

The following examples are presented to demonstrate the invention. Theexamples are illustrative only and are not intended to limit the scopeof the invention in any way.

EXAMPLE 1

This example shows that administering an effective amount of succinicacid disodium salt hexahydrate to streptozotocin-induced rats iseffective in treating insulin resistance.

Animals. Male albino Wistar rats 8-10 weeks of age 200-250 grams of bodyweight were used. The rats were housed at the temperature of 18±21° C.on a 12 hour light-dark cycle. Rats were fed on a stock laboratory diet(59% carbohydrates; 17% protein; 3% fat; 21% minerals, water, cellulose)and allowed water ad libitum. The streptozotocin (Sigma, St. Louis, Mo.,USA) solved in citrate buffer (0.05M, pH 5.5) was injected into tailvein of male albino Wistar rats in a dose of 35 mg per kg of animal bodyweight to induce decompensated insulin resistance. The rats with levelsof glucose more than 14.0 mmol/l were used in the experiment one weekafter the streptozotocin injection.

Assays. Plasma free fatty acids levels were determined by enzymaticmethod with a commercially available kit (Waho Chemicals Gmbh, Neuss,Germany) with Multistat 3 centrifugal analyzer (InstrumentationLaboratories, Lexington, USA).

Serum glucose concentrations were determined by the glucose oxidasemethod with a kit (Lachema, Slov.) with glucose analyzer (Beckman,Fullerton, Calif., USA).

Plasma insulin concentrations were determined by a double-antibodyradioimmunoassay kit (Kabi Pharmacia Diagnostics, Uppsala, Sweden) usinga rat insulin standard (Novo Research Institute, Bagsvard, Denmark).

Plasma triglycerides and cholesterol concentrations in High DensityLipoprotein (HDL) and Low Density Lipoprotein (LDL) were determined byenzymatic methods with kits (Boeringher Mannheim, Mannheim, Germany)with Multistat 3 F/LS apparatus (Instrumentation Laboratories,Lexington, USA).

Procedure. Streptozotocin-induced rats were assigned to two groups: acontrol rats (six rats) and experimental rats (fifteen rats).Experimental rats received daily injection (subcutaneously, 0.5 ml at09.00 h) of water solution of succinic acid disodium salt hexahydrate ina dose of 5 mg per kg of body weight for period of 7 days.

Plasma free fatty acid levels (FFA), plasma Insulin levels and serumglucose levels were measured in rats by tail clipping method at zero day(before treatment), at third, fifth and seventh days (treatment period),and at tenth, fifteen, twentieth, twenty fifth and thirtieth days(after-treatment period).

The results are demonstrated in Table 1 through 3.

TABLE 1 Mean plasma FFA levels in experimental rats in comparison withcontrol rats. FFA, mmol/l Days Control rats Experimental rats Beforetreatment  0 0.31 ± 0.02 0.35 ± 0.03 Treatment  3 0.30 ± 0.03 0.32 ±0.04 period  5 0.31 ± 0.05 0.25 ± 0.06  7 0.29 ± 0.04 0.18 ± 0.05 After-10 0.31 ± 0.03 0.20 ± 0.06 treatment 15 0.28 ± 0.02 0.15 ± 0.03 period20 exitus  0.10 ± 0.05* 25 letalis  0.11 ± 0.04* 30  0.13 ± 0.04**Denotes statistically significant means (p < 0.05).

TABLE 2 Mean plasma insulin and serum glucose levels in experimentalrats. Days Insulin, ng/ml Glucose, mmol/l Before treatment  0 11.0 ±0.7  15.7 ± 2.6  Treatment  3 10.2 ± 1.1  15.8 ± 3.1  period  5 7.4 ±0.8 13.0 ± 2.4   7 4.2 ± 0.7 10.0 ± 1.2  After-treatment 10 3.1 ± 0.810.1 ± 2.0* period 15 2.4 ± 0.4 8.1 ± 1.1 20 2.1 ± 0.4 6.6 ± 0.8 25 2.0± 0.3  5.7 ± 0.5* 30 2.1 ± 0.3 5.4 ± 0.7 *Denotes statisticallysignificant means (p < 0.05).

TABLE 3 Mean plasma insulin and serum glucose levels in control rats.Days Insulin, ng/ml Glucose, mmol/l Before treatment  0 10.3 ± 1.2  15.7± 2.6 Treatment  3 9.6 ± 1.4 15.1 ± 1.8 period  5 9.0 ± 0.8 14.7 ± 1.4 7 7.0 ± 1.3 13.3 ± 1.4 After-treatment 10 9.3 ± 0.8 14.1 ± 0.6 period15 10.4 ± 1.4  13.0 ± 0.8 20 exitus exitus 25 letalis letalis 30

The data of the Table 1 through 3 demonstrate that treating insulinresistant rats by the effective amount of succinic acid disodium salthexahydrate causes a significant improving in insulin sensitivity incomparison with control insulin resistant rats that manifests itself inlowering of pathologically elevated plasma free fatty acid levels,plasma insulin and serum glucose levels. Maximal efficacy of thetreating is achieved in the after-treatment period.

Administration of succinic acid disodium salt hexahydrate to healthyrats causes no changes in plasma free fatty acid levels (0.08±0.03mmol/l), in serum glucose (4.8±0.4 mmol/l) and plasma insulin levels(3.4±0.6 ng/ml) during thirty days of the experiment analogous todescribed above.

EXAMPLE 2

This example shows that administering to non-insulin dependent diabetichumans an effective amount of succinic acid is an effective therapy fortreating insulin resistance.

Patients. Twelve non-insulin dependent diabetic humans were studied.Non-insulin Dependent Diabetes Mellitus (NIDDM) was diagnosed in thehumans according to the World Health Organisation criteria and had beenpresented for minimum 5 years. The NIDDM humans were metabolicallystable and had glucose levels more than 12.8 mmol/l. Six patients weretaking oral sulphonylurea hypoglicemic drug glibenclamide (rec. INN).None of the humans were undergoing hypolipidemic therapy. The humans hadno additive metabolic disorders.

The following table summarizes the characteristics of the humans:

Mean ± SD Number of humans 12 Age, years 65 ± 3  Gender, men/women 4/8BMI 25.1 ± 0.8  kg/m² Fasting plasma glucose 13.7 ± 0.6  mmol/l PlasmaFFA 0.240 ± 0.044 mmol/l Plasma insulin 140 ± 23  pmol/l Plasma LDLcholesterol 4.8 ± 0.3 mmol/l Plasma HDL cholesterol 0.6 ± 0.4 mmol/lTotal cholesterol 6.8 ± 0.4 mmol/l Plasma triglycerides 2.7 ± 0.3 mmol/lGlycated hemoglobin 11.4 ± 1.2  %

Assays. Assays were used as described in the example 1 of the invention.Plasma insulin concentrations were determined by a double-antibodyradioimmunoassay kit (Kabi Pharmacia Diagnostics, Uppsala, Sweden).

Procedure. Pharmaceutical grade succinic acid in a unit dosage form of100 mg per gelatin capsule was used. All patients received succinic acidorally in daily dose of 200 mg to 400 mg per day for period of 3 to 7days.

Plasma free fatty acid levels, insulin levels and serum glucose levels,plasma high density lipoprotein cholesterol (HDL-cholesterol), lowdensity lipoprotein cholesterol (LDL-cholesterol) and triglycerides weremeasured in humans at zero day (before treatment ), at third and fifthdays (treatment period), and at tenth, fifteen twentieth, twenty fifththirtieth and fortieth days (after-treatment period). The resulted aredemonstrated in Tables 4 through 6.

TABLE 4 Mean plasma FFA levels in NIDDM humans treated by succinic acidDays FFA, mmol/l Before treatment  0 0.240 ± 0.044 Treatment period  30.250 ± 0.071  5 0.195 ± 0.064 After-treatment 10 0.184 ± 0.035 period15 0.157 ± 0.032 20 0.161 ± 0.034 25  0.113 ± 0.046* 30  0.086 ± 0.035*40 0.100 ± 0.022 *Denotes statistically significant means (p < 0.05).

TABLE 5 Mean plasma insulin and serum glucose levels in NIDDM humanstreated by succinic acid. Days Insulin, pmol/l Glucose, mmol/l Beforetreatment  0 140 ± 23 14.8 ± 1.4 Treatment  3 — 14.5 ± 1.4 period  5 —14.9 ± 1.5 After-treatment 10 134 ± 27 13.0 ± 2.0 period 15 — 13.1 ± 0.820 124 ± 17 11.0 ± 1.0 25 —  9.4 ± 1.3 30 118 ± 21  7.1 ± 0.6 40 112 ±14  5.8 ± 1.1

The data of the Tables 4 and 5 demonstrate that the treating of thenon-insulin dependent diabetic humans by effective amount of succinicacid causes an improving in insulin sensitivity that manifests itself inlowering of free fatty acid levels, insulin and glucose levels. Maximalefficacy of the treating is achieved in the after-treatment period.

TABLE 6 Mean Plasma Low Density Lipoprotein cholesterol (LDL), HighDensity Lipoprotein cholesterol (HDL), and Triglycerides levels in NIDDMhumans treated by succinic acid. Triglycerides, Days LDL, mmol/l HDL,mmol/l mmol/l Before  0 4.8 ± 0.3 0.6 ± 0.4 2.7 ± 0.3 treatmentTreatment  3 4.9 ± 0.4 0.7 ± 0.2 2.8 ± 0.6 period  5 4.7 ± 0.2 0.8 ± 0.22.7 ± 0.3 After 10 4.3 ± 0.6 1.2 ± 0.4 2.5 ± 0.3 treatment 15 4.0 ± 0.31.2 ± 0.3 2.4 ± 0.4 period 20 3.5 ± 0.4 1.2 ± 0.4 1.8 ± 0.4 25 3.4 ± 0.3 1.3 ± 0.2* 1.3 ± 0.2 30 3.4 ± 0.2  1.5 ± 0.2*  1.1 ± 0.1* 40 3.5 ± 0.41.3 ± 0.2 1.4 ± 0.2 *Denotes statistically significant means (p < 0.05).

The data of the Table 6 demonstrate that increasing of insulinsensitivity in non-insulin dependent diabetic humans treated byeffective amount of succinic acid causes to reducing plasmatriglycerides and low density lipoprotein cholesterol, and increasingplasma high density lipoprotein cholesterol, especially is in theafter-treatment period.

Thus, the administration of succinic acid or salt thereof is aneffective therapy for treating of insulin resistance.

We claim:
 1. A method of treating insulin resistance in a mammal, whichcomprises administering to a mammal in need thereof an effective amountof succinic acid or a pharmaceutically acceptable salt thereof.
 2. Themethod as claimed in claim 1 wherein the effective amount of succinicacid, or a pharmaceutically acceptable salt thereof, is 0.1 milligram to50 milligrams per kilogram of body weight per day.
 3. The method asclaimed in claim 2 wherein the succinic acid or a pharmaceuticallyacceptable salt thereof is administered orally, or parenterally, ortopically, or rectally.
 4. The method as claimed in claim 2 wherein thesuccinic acid or a pharmaceutically acceptable salt thereof isadministered for a period of 1 day or longer.
 5. The method as claimedin claim 2 wherein the mammal is human.
 6. The method as claimed inclaim 5 wherein the human is a non-insulin dependent diabetic human. 7.The method as claimed in claim 1 wherein the effective amount ofsuccinic acid or a pharmaceutically acceptable salt thereof is 1milligram to 20 milligrams per kilogram of body weight per day.
 8. Themethod as claimed in claim 7 wherein the succinic acid or apharmaceutically acceptable salt thereof is administered orally, orparenterally, or topically, or rectally.
 9. The method as claimed inclaim 7 wherein the succinic acid or a pharmaceutically acceptable saltthereof is administered for a period of 1 day or longer.
 10. The methodas claimed in claim 7 wherein the mammal is human.
 11. The method asclaimed in claim 10 wherein the human is a non-insulin dependentdiabetic human.
 12. The method as claimed in claim 1 wherein thesuccinic acid or a pharmaceutically acceptable salt thereof isadministered orally, or parenterally, or topically, or rectally.
 13. Themethod as claimed in claim 12 wherein the succinic acid or apharmaceutically acceptable salt thereof is administered for a period of1 day or longer.
 14. The method as claimed in claim 12 wherein themammal is human.
 15. The method as claimed in claim 14 wherein the humanis a non-insulin dependent diabetic human.
 16. The method as claimed inclaim 1 wherein the succinic acid or a pharmaceutically acceptable saltthereof is administered for a period of 1 day or longer.
 17. The methodas claimed in claim 16 wherein the succinic acid or a pharmaceuticallyacceptable salt thereof is administered for a period of 3 to 7 days. 18.The method as claimed in claim 17 wherein the mammal is human.
 19. Themethod as claimed in claim 18 wherein the human is a non-insulindependent diabetic human.
 20. The method as claimed in claim 16 whereinthe mammal is human.
 21. The method as claimed in claim 20 wherein thehuman is a non-insulin dependent diabetic human.
 22. The method asclaimed in claim 1 wherein the mammal is human.
 23. The method asclaimed in claim 22 wherein the human is a non-insulin dependentdiabetic human.